Inflammation is a localized protective response elicited by tissues in response to injury, infection, or tissue destruction resulting in the destruction of the infectious or injurious agent and isolation of the injured tissue. A typical inflammatory response proceeds as follows: recognition of an antigen as foreign or recognition of tissue damage, synthesis and release of soluble inflammatory mediators, recruitment of inflammatory cells to the site of infection or tissue damage, destruction and removal of the invading organism or damaged tissue, and deactivation of the system once the invading organism or damage has been resolved. In many human diseases with an inflammatory component, the normal, homeostatic mechanisms which attenuate the inflammatory responses are defective, resulting in damage and destruction of normal tissue.
Cell-cell interactions are involved in the activation of the immune response at each of the stages described above. One of the earliest detectable events in a normal inflammatory response is adhesion of leukocytes to the vascular endothelium, followed by migration of leukocytes out of the vasculature to the site of infection or injury. The adhesion of these leukocytes, or white blood cells, to vascular endothelium is an obligate step in the migration out of the vasculature (Harlan, J. M., Blood 1985, 65, 513-525). This response is mediated by the interaction of adhesion molecules expressed on the cell surface of leukocytes and vascular endothelial cells. Very late antigen-4 (also called VLA-4, .alpha.4.beta.1 or CD49d/CD29) is a homodimeric adhesion receptor which is composed of noncovalently linked .alpha. and .beta. subunits and serves to mediate leukocyte adhesion to vascular cell adhesion molecule-1 (VCAM-1) which is expressed on cytokine-stimulated endothelial cells. This interaction between VCAM-1 and VLA-4 contributes to leukocyte extravasation in acute and chronic inflammatory conditions including multiple sclerosis (MS), rheumatoid arthritis, asthma, psoriasis and allergy.
Fibronectin is also a ligand for VLA-4. Fibronectin plays an important role in many processes including embryonic development, wound healing and tumor cell metastasis (Guan, J.-L. and Hynes, R. O., Cell 1990, 60, 53-61).
VLA-4 is a heterodimer of an .alpha.4 integrin and .beta.1 integrin. The .alpha.4 integrin can also heterodimerize with a .beta.7 integrin chain to form integrin .alpha.4.beta.7 which is known as a mucosal homing receptor because its primary ligand is the mucosal vascular addressing MadCAM-1. Integrin .alpha.4.beta.7 identifies a subset of memory T cells with a tropism for the intestinal tract, whereas integrin .alpha.4.beta.1 (VLA-4) is constitutively expressed on most mononuclear leukocytes, but not on circulating neutrophils. The interaction of VCAM-1 with VLA-4 suggests that VLA-4 is a potential therapeutic target for inflammatory diseases, including atherosclerosis, allergy and asthma, arthritis, and tumor cell metastasis (Kassner, P. D., et al, Adv. Exp. Med. Biol. 1992, 323, 163-170). VLA-4 has also been found to play a role in promoting adhesion (i.e., retention) of hemopoietic stem cells in the bone marrow (Papayannopoulou and Nakamoto, Proc. Natl. Acad. Sci. U.S.A. 1993, 90, 9374-9378).
Asthma is an inflammatory disease associated with eosinophil infiltration into the lung. VLA-4 is expressed on eosinophils. Metzger, W. J. (Springer Semin. Immunopathol. 1995, 16, 467-478) used a rabbit model of asthma to demonstrate that both an anti-VLA-4 antibody and a CS-1 peptide could reduce eosinophil infiltration into the lung and reduce the development of asthma.
Rheumatoid arthritis is another disease associated with inflammation. Muller-Ladner, U., et al., (J. Rheumatology 1997, 24, 1873-1880) found that the alternatively spliced form of fibronectin containing CS-1 was expressed in the rheumatoid synovium. Additionally, they found that not only did expression of fibronectin result in recruitment of VLA-4 expressing cells, but fibroblasts in the rheumatoid synovium expressed VLA-4. Seiffge, D. (J. Rheumotology 1996, 23, 2086-2091) used a rat model for arthritis to show that a monoclonal antibody to the .alpha.4 chain of VLA-4 resulted in an improvement of symptoms.
VLA-4 also plays a role in a number of autoimmune diseases. Marazuela, M., et al., (Eur. J. Immunol. 1994, 24, 2483-2490) found elevated expression of both the VLA-4/VCAM-1 and LFA-1/ICAM-1,3 pathways in Graves' disease and Hashimoto's thyroiditis, suggesting that both play a role in these diseases. VLA-4 may also play a role in multiple sclerosis. Antibodies to VLA-4 have been found to prevent experimental autoimmune encephalomyelitis (EAE), an experimentally induced disease with similarities to multiple sclerosis (Yednock, T. A., et al., Nature 1992, 356, 63-66). Elevated expression levels of VLA-4 were detected in a patient with systemic lupus erythematosus (Takeuchi, T., et al., Clin. Rheumatology 1995, 14, 370-374). VLA-4 is involved in cellular responses to two surgical procedures, transplantation and vascular reconstructive procedures. Allograft rejection is a common response to transplantation of a foreign tissue. CS-1 peptides have been found to prevent both acute rejection (Coito, A. J., et al., Transplantation 1998, 65, 699-706) and chronic rejection (Korom, S., et al., Transplantation 1998, 65, 854-859) by blocking VLA-4 binding to fibronectin. During vascular reconstructive surgery, a common cause of failure is intimal hyperplasia which results from the accumulation of monocytes and lymphocytes. In a baboon model, Lumsden, A. B., et al.,(J. Vasc. Surg. 1997, 26, 87-93) demonstrated that an anti-VLA-4 antibody reduced intimal hyperplasia.
VLA-4 also plays a role in tumor cell metastasis. In metastasis, tumor cells must cross the extracellular matrix, enter the circulatory system and invade into new tissue. Bao, L. et al., (Differentiation 1993, 52, 239-246) detected VLA-4 expression of many human tumor cell lines, including a breast carcinoma, melanoma, and renal carcinoma, and found that the presence of VLA-4 correlated well with metastatic potential. Kawaguchi, S. et al., (Jpn. J. Cancer Res. 1992, 83, 1304-1316) transfected a cDNA encoding the .alpha.4 subunit of VLA-4 into a human fibrosarcoma cell line. These cells overexpressed VLA-4 and showed increased in vitro invasive ability. Augmentation of metastasis by IL-1 (Garofalo, A.,et al., Cancer Res. 1995, 55, 414-419) or TNF-.alpha. (Okahara, H., et al., Cancer Res. 1994, 54, 3233-3236) has been shown to involve the interaction between VLA-4 and VCAM-1. These authors suggest that a therapy directed towards inhibiting this interaction would be useful in reducing the risk of metastasis with conditions associated with high serum concentrations of TNF-.alpha., including cachexia, sepsis, surgical stress, or TNF-.alpha. therapeutic applications. Because tumor cells often secrete IL-1 and TNF-.alpha., such a therapy may be useful in reducing the risk of metastasis associated with such tumor cells.
VLA-4 is involved in promoting retention of hemopoietic progenitor cells in the bone marrow. Antibodies to integrin .alpha.4 (but not integrin .beta.2) have been found to selectively mobilize progenitor/stem cells into the bloodstream (Papayannopoulou and Nakamoto, Proc. Natl. Acad. Sci. U.S.A. 1993, 90, 9374-9378). This mobilization is of clinical relevance in the field of bone marrow transplantation as it obviates the need for marrow harvesting by making hemopoietic progenitor cells available in the circulating blood.
While steroids and other antiinflammatory drugs are effective in treating inflammatory diseases and conditions, long-term usage often leads to side effects such as increased risk of infection caused by impairment of phagocytic leukocyte migration and function. There is some concern that inhibition of the function of the .beta.1 integrin chain may be associated with increased susceptibility to infections, as demonstrated by a .beta.1 (also called CD18) monoclonal antibody in rabbits (Foster, C. A., 1996, J. Allergy Clin. Immunol., 98, 270-277). It is believed that selective inhibition of the .alpha.4 chain may be a more desirable approach. Inhibition of the .alpha.4 chain is believed likely to reduce levels of the VLA-4 heterodimer as well as the .alpha.4.beta.7 heterodimer.
Potential therapeutic interventions targeting VLA-4 include monoclonal antibodies, and peptide antagonists. Leger, O. J. P., et al. (Human Antibodies 1997, 8, 3-16) describe a monoclonal antibody against VLA-4 that is in phase II clinical trials for multiple sclerosis. CS-1 peptide antagonists have been described by Jackson, D. Y., et al. (J. Med. Chem. 1997, 40, 3359-3369).
Hayashi et al. (Cell Struct. Funct. 1991, 16, 241-249) have used a vector expressing RNA complementary to chicken integrin .beta.1 to reduce integrin .beta.1 expression, resulting in altered cell attachment and shape.
Antisense oligonucleotides targeted to various integrins have been used as tools to dissect the functional interactions of integrins in complex settings. Lallier and Bronner-Fraser (Science, 1993, 259, 692-695) have used phosphorothioate oligonucleotides targeted to conserved and nonconserved regions of chick .beta.1, human .alpha.4, rat .alpha.1 and human .alpha.5 integrins to determine the effects of these integrins on cell attachment. These same oligonucleotides were also injected into cranial neural crest migratory pathways in avian embryos, and it was demonstrated that those oligonucleotides that inhibited cell attachment in vitro also caused neural crest and/or neural tube abnormalities in vivo (Kil et al., Devel. Biol. 1996, 179,91-101).
EP patent application 688 784 (Carolus et al.) discloses 3' derivatized oligonucleotide analogs, including one sequence targeted to the .beta.1 subunit of VLA-4.
Antisense oligonucleotides are believed to represent a useful means of modulating the expression of integrin .alpha.4 and of treating diseases associated with its expression.